1. Field of the Invention
The present invention relates to an electron emitter applicable to electron beam sources for use in various devices and apparatus that utilize electron beams, such as displays (e.g., field emission display (FEDs)), electron beam irradiation apparatus, light sources, electronic-component-manufacturing apparatus, and electronic circuit components.
2. Description of the Related Art
As is generally known, the aforementioned electron emitter is configured such that a predetermined electric field is applied to an emitter section (electron emission section) in a vacuum having a predetermined vacuum level, whereby electrons are emitted from the emitter section. In application to an FED, a plurality of electron emitters are two-dimensionally arrayed on a substrate formed of, for example, glass or ceramic material. In addition, a plurality of phosphors corresponding to the electron emitters are arrayed with a predetermined gap therebetween. Among the two-dimensionally arrayed electron emitters, certain electron emitters are selectively driven so as to emit electrons therefrom. The emitted electrons fly through the aforementioned gap and collide with phosphors corresponding to the driven electron emitters. The phosphors hit by the electrons fluoresce, thereby displaying a desired image.
Conventionally known electron emitters include an electron emitter having an emitter section formed of a dielectric material (piezoelectric material). Such an electron emitter is called a “piezoelectric-film-type electron emitter.” This type of electron emitter is produced at low cost, and therefore is suitable for use in an FED, in which, as described above, numerous electron emitters are two-dimensionally arrayed on a substrate having a relatively large area. Conventional piezoelectric-film-type electron emitters are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 2004-146365 and 2004-172087.
Such a conventional piezoelectric-film-type electron emitter is configured such that a cathode electrode covers a portion of the top surface of an emitter section formed of a dielectric material, and an anode electrode is provided on the bottom surface of the emitter section, or on the top surface of the emitter section at a position a predetermined distance away from the cathode electrode. Specifically, the electron emitter is configured such that an exposed portion of the top surface of the emitter section at which neither the cathode electrode nor the anode electrode is formed is present in the vicinity of a peripheral edge portion of the cathode electrode (the exposed portion plays an important role for electron emission in the emitter section, and this portion will be called an “electron emission region”).
The conventional electron emitter is operated as follows. In the first stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is higher in electric potential. An electric field induced by the applied voltage brings the electron emission region of the emitter section into a predetermined polarization state. In the second stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is lower in electric potential. At this time, primary electrons are emitted from the peripheral edge portion of the cathode electrode, and the polarization of the emitter section is inverted. The primary electrons collide with the electron emission region of the polarization-inverted emitter section, whereby secondary electrons are emitted from the electron emission region. The secondary electrons fly in a predetermined direction by means of an externally applied, predetermined electric field; i.e., the electron emitter emits electrons.